(1) Field of the Invention
The present invention relates to drive units for image capturing devices and control method thereof. The invented drive unit generates motion of the image capturing device or multiple image capturing devices by using twisted strings mechanism.
(2) Description of Related Art
Image capturing devices such as semiconductor cameras are used for surveillance and for robotic eyes, particularly in humanoid robots. Image capturing devices are immovably fixed to the base or are movable with the goal to increase visibility range of the device. Motion of the device can be generated by various types of motors that are directly coupled to the device (for example U.S. Pat. No. 6,628,338 B1) or coupled by gear and/or link mechanisms (for example U.S. Pat. No. 7,777,810 B2).
Particularly in the case of robotic eyes, fast motion of the image capturing device is needed to achieve motion that is similar to a human or live being's eye. A large torque is needed to realize fast motion, therefore, in the case of directly coupled motors, the motors become large and thus heavy. On the other hand, in the case of gear reducers used with the motor, the weight and size of the motors can be reduced, but the mechanisms generate noise, and the motion appearance is “too mechanical” to be suitable for humanoid robots, which should resemble eye motion of a live being.
What is still needed, is a drive unit for image capturing device that achieves motion performance similar to a human eye, that is, maximum angular speed of 900 angular degrees per second, operates quietly, is of small size and lightweight, and resembles motion of an eye of a live being.